US4862008A - Method and apparatus for optical alignment of semiconductor by using a hologram - Google Patents

Method and apparatus for optical alignment of semiconductor by using a hologram Download PDF

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Publication number
US4862008A
US4862008A US07/213,141 US21314188A US4862008A US 4862008 A US4862008 A US 4862008A US 21314188 A US21314188 A US 21314188A US 4862008 A US4862008 A US 4862008A
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Prior art keywords
alignment
hologram
light
wafer
illumination
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Yoshitada Oshida
Naoto Nakashima
Yasuhiro Yoshitake
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Hitachi Ltd
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Hitachi Ltd
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F9/00—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
    • G03F9/70—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography

Definitions

  • the present invention relates to method and apparatus for exposing a fine pattern such as a semiconductor to light, and more particularly to method and apparatus of light exposure which uses a short wavelength light for focusing and light exposure, detects an alignment mark on an article to be exposed to the light by a light having a longer wavelength than that of the exposure light through an exposure focusing system.
  • a wavelength thereof is one half of that of a visible band (450 nm ⁇ 700 nm) and several kinds of glass materials are required for exposing reduction lenses (hereinafter exposure lens and reduction lens are used synonymously). As a result, it is not possible to pay attention to a focusing characteristic to a wavelength other than the exposure light wavelength.
  • a focusing system comprises quartz glass or a combination of quartz glass and fluorite.
  • an alignment light which is a visible light such as argon (Ar) laser (wavelength 515 nm) or helium-neon (He-Ne) laser (543.5 nm, 633 nm)
  • Ar argon
  • He-Ne helium-neon
  • a focusing system for the registration mark (off-axis alignment system) is used separately from the reduction lens in order to effect alignment.
  • an ultraviolet ray (or far ultraviolet ray) which is the same or close to the wavelength of the exposure light is used together with the reduction lens to effect the alignment.
  • TTL detection exposing reduction lens
  • the above object is achieved by a method for optical alignment of a semiconductor which irradiates an exposure light to a mark having a fine pattern drawn thereon.
  • a transmitted light therefrom is directed by an exposure lens as an image of the pattern on a wafer
  • an alignment mark on the wafer is irradiated by an alignment light having a different wavelength than that of the exposure light.
  • a reflected light therefrom is detected through the exposure lens to detect the position of the alignment mark on the wafer.
  • a halogram is used in at least one of irradiation and detection to compensate for a wavefront aberration of the exposure lens at the alignment wavelength.
  • the hologram is used in at least one of irradiation and detection or the alignment mark on the wafer.
  • the hologram permits recording of not only information relating to an intensity of light after reflection by or transmission through an object but also information relating to a phase (wavefront). Accordingly, by recording the wavefront aberration of the reduction lens at the alignment wavelength into the hologram and compensating for the aberration of the reduction lens at the alignment wavelength by using the hologram, it is possible to irradiate the alignment light to the alignment mark of desired shape and dimension on the wafer through the reduction lens, and the alignment light reflected by the alignment mark can be detected with a high focusing ability.
  • FIG. 1A shows an overall construction of one embodiment of an optical aligner for a semiconductor of the present invention
  • FIG. 1B shows a detection optical system of FIG. 1A
  • FIG. 1C shows a detection signal waveform detected by a detector of FIG. 1A
  • FIG. 1D shows an enlarged perspective view of an illumination light for illuminating a wafer of FIG. 1A
  • FIG. 2A shows an overall construction of another embodiment of the optical aligner for the semiconductor of the present invention
  • FIG. 2B shows an enlarged perspective view of an illumination light for illuminating a wafer of FIG. 2A
  • FIG. 3A shows an overall construction of other embodiment of the optical aligner for the semiconductor of the present invention
  • FIG. 3B shows an enlarged perspective view of an illumination light for illuminating a wafer of FIG. 3A
  • FIG. 4A shows an overall construction of other embodiment of the optical aligner for the semiconductor of the present invention
  • FIG. 4B shows an enlarged perspective view of an illumination light for illuminating a wafer of FIG. 4A
  • FIG. 5A shows an overall construction of other embodiment of the optical aligner for the semiconductor of the present invention
  • FIG. 5B shows an enlarged perspective view of an illumination light for illuminating a wafer of FIG. 5A
  • FIG. 5C shows a hologram recording medium
  • FIG. 6A illustrates a method for forming the hologram shown in FIG. 5A
  • FIG. 6B shows an illumination light for illuminating a slit of FIG. 6A
  • FIG. 7 shows other embodiment of a detection optical system of the present invention
  • FIG. 8A shows an overall construction of other embodiment of the detection optical system of the present invention.
  • FIG. 8B illustrates a method for forming a hologram of FIG. 8A
  • FIG. 8C illustrates a principle of a wafer illumination system of FIG. 8A
  • FIG. 9A shows an overall construction of other embodiment of the detection optical system of the present invention.
  • FIG. 9B shows a detection signal waveform detected by a detector of FIG. 9A
  • FIG. 9C shows an enlarged perspective view of an illumination light for illuminating a wafer of FIG. 9A
  • FIG. 10A shows an overall construction of other embodiment for forming a hologram in the present invention
  • FIG. 10B illustrates a reproduced light of FIG. 10A
  • FIG. 10C shows an enlarged view of an illumination light for illuminating an alignment mark in a wafer of FIG. 10B
  • FIG. 10D shows an enlarged view of a pinhole plate of FIG. 10A
  • FIG. 11A shows a relationship between a thickness of a resist layer and an interference strength in one embodiment of 2-wavelength and 2-angle illumination of the present invention
  • FIG. 11B shows a galvano-mirror drive timing chart in the embodiment of the 2-wavelength and 2-angle illumination of the present invention
  • FIG. 11C shows a relationship between a polarization angle and a time sequence in the embodiment of the 2-wavelength and 2-angle illumination of the present invention
  • FIG. 12A illustrates irradiation and reflection of an illumination light to and by an alignment mark on a wafer in other embodiment of the 2-wavelength and 2-angle illumination of the present invention
  • FIG. 12B shows a galvano-mirror drive timing chart in the other embodiment of the 2-wavelength and 2-angle illumination of the present invention
  • FIG. 12C shows a timing chart of the 2-wavelength and 2-angle illumination in the other embodiment of the 2-wavelength and 2-angle illumination of the present invention
  • FIG. 13 shows a relationship between a thickness of a resist layer and an interference strength in FIG. 12,
  • FIGS. 14A to 14C illustrate reduction of asymmetricity of a detection pattern detected by application of the resist layer near an edge of an alignment mark
  • FIG. 14A shows ununiformity in application of the resist layer
  • FIG. 14B shows a waveform of a simple 2-wavelength detection pattern
  • FIG. 14C shows a waveform of a 2-wavelength detection pattern of the present invention
  • FIG. 15 shows a method for forming an aberration compensation hologram and a method for using the hologram in the present invention
  • FIG. 16A shows an overall construction of an optical aligner for a semiconductor of the present invention which uses a reflection type hologram
  • FIG. 16B illustrates a reproduced light of FIG. 16A
  • FIG. 16C illustrates a method for detecting a reflected light of FIG. 16A.
  • FIGS. 15A, 15B and 15C Constructions, concept and functions of the alignment illumination means and detection means of the optical aligner which uses the hologram in accordance with the present invention are explained with reference to FIGS. 15A, 15B and 15C.
  • FIG. 15A shows a perspective view illustrating a method for forming a hologram.
  • a reduction lens 3 made of quartz glass has a high resolution focusing relationship between a wafer surface SW and a reticle surface SR for an exposure light (248.5 nm).
  • an image of a slit 201(A) on the wafer surface SW is not formed on the reticle surface SR but it is formed at a position largely spaced from the reticle surface SR.
  • a resolution of the image of the slit 201(A) is significantly deteriorated, it is almost impossible from a standpoint of precision to detect the wafer image by using the image of the slit to effect the alignment.
  • a mask 200 is arranged at a position corresponding to the wafer plane SW to the reduction lens 3.
  • the slit 201(A) having a width of approximately 1 ⁇ m is formed on the mask 200, and the slit 201(A) is irradiated by a laser beam 503" (or 513") having the same wavelength as the alignment light.
  • a cylindrical lens 210 is used to efficiently irradiate the laser beam 503" (or 513") to the slit 201(A).
  • the laser beam 503" (or 513") of the alignment waveform which has passed through the slit 201(A) is emitted as if there were a light source having the width of 1 ⁇ m on the wafer surface SW.
  • the laser beam 503' (or 513") passes through the reduction lens 3, it does not form the image of the slit 201(A) on the plane SR corresponding to the reticle surface but it forms a defocused image at a position A 1 on an extended line.
  • the slit image is not necessarily a real image but it may be a virtual image. The method of the present invention is applicable even in such a situation.
  • the laser beam 503" (or 513") directed to the position A 1 is reflected by a mirror or half-mirror 51 to form a mirror image of the position A 1 at a position A 1 '.
  • a hologram recording medium 8 is arranged in a light path of the reflected light and a reference light 501' is superimposed to a position 81' through which the laser beam 503' (or 513') reflected by the recording medium 8 passes to record a hologram interference fringe onto the hologram recording medium 8.
  • the reference beam 501' is formed by using a focusing lens 80 so that the laser beam 503' (or 513') is focused at a point O 1 .
  • the first hologram 81 formed at a position 81 through which the reflected laser beam 503' (or 513') passes is formed by using the laser beam 503" (or 513") as an object light, whose primary light beam is normal to the slit 201. Accordingly, the object light used to form the first hologram 81 is perfectly reproduced by reproducing the first hologram 81 by the reproducing light which is focused at the point O 1 (emitted from the point O 1 ) as shown in FIG. 15B.
  • the reproducing (diffraction) light of the first hologram 81 forms an aperture image of the slit 201 having the width of 1 ⁇ m at the position corresponding to the position of the slit 201 as shown in FIG. 15A.
  • the hologram reproduced light can illuminate in a narrow slit of a resolution width at a limit of diffraction determined by the number of aperture of the exposure lens and the wavelength. Accordingly, when the alignment mark 21 on the wafer is moved to the position corresponding to the position of the slit 201, it is possible to illuminate the alignment mark 21 in a very limited area as shown in FIG. 15B.
  • a second hologram 82 is recorded on the hologram recording medium 8.
  • the second hologram 82 is formed in the following manner.
  • the illumination light 503" to the slit 201 is emitted with a primary optical axis thereof being directed at an incident angle ⁇ to the slit surface SW.
  • the transmitted light 503' (or 513') from the slit 201 passes through the reduction lens 3 and the mirror 51 and is directed to the position 82' of the hologram recording medium 8 where it is superimposed to form an interference fringe with the reference light 511' focused at the point O D .
  • the second hologram 82 is formed at the position 82'.
  • the second hologram 82 is used to detect the diffracted light (diffraction angle ⁇ ) from the alignment mark 21 (periodic structure as shown in FIG. 1D) on the wafer as shown in FIG. 15C.
  • the laser illumination light 503 (see FIG. 15B) to the alignment mark 21 on the wafer is formed by the first hologram 81, and the wafer illumination light 502 generated by the first hologram 81 illuminates the wafer 2 normally to the plane of the alignment mark 21 of the wafer 2.
  • the diffraction angle ⁇ from the alignment mark 21 having the periodic structure (pitch ⁇ ) reflects at ##EQU1## and the detection light 502 transmitted through the reduction lens 3 and the mirror 51 is directed to the second hologram 82.
  • the diffracted light 511 from the second hologram 82 is focused at the focusing point O D of the reference light 511' used to form the second hologram 82, as shown in FIG. 15C.
  • the alignment mark 21 can be detected by arranging the detector (not shown) at the focusing point O D .
  • FIGS. 1A to 1D One embodiment of the present invention is now explained with reference to FIGS. 1A to 1D.
  • numeral 1 denotes a reticle (mask)
  • numeral 10 denotes a master pattern of a circuit pattern
  • numeral 2 denotes a wafer
  • numeral 20 denotes a field which is exposed to light at one time and which contains one to several chips
  • numeral 21 denotes an alignment mark of the wafer 2.
  • the master pattern 10 of the circuit pattern on the reticle 1 is reduced by a reduction lens 3 and focused onto the field 20 on the wafer 2 by an exposure light (not shown).
  • Numeral 4 denotes an exposure light source.
  • the alignment mark 21 has an x-axis alignment mark 21x a y-axis alignment mark 21y for each exposure field 20 on the wafer 2.
  • the alignment marks 21x and 21y are detected by separate detection optical systems, although only an x-axis detection optical system 50 is shown.
  • the x-axis detection optical system 50 directs the alignment laser beam 501 to the alignment mark 21 on the wafer and detects the reflected light 503 (or 513) and it comprises a mirror 51.
  • a hologram 8 an apertured mirror 52, condenser lenses 53 and 54 and a photo-detector 55.
  • the laser beam 501 emitted from the alignment laser light source (not shown) is focused to the aperture 521 of the apertured mirror 52 by the condenser lens 53, and the scattering laser beam 501 transmitted through the aperture 521 is directed to the first hologram 81 recorded on the hologram recording medium 8.
  • the diffracted light 502 from the first hologram 81 passes through the mirror 51 and the reduction lens 3 and the light 503 in a slit shape having a width of approximately 1 ⁇ m is irradiated onto the wafer 2.
  • the alignment mark 21 of the periodic structure having a plurality of recessed patterns 210 arranged at a pitch ⁇ is recorded on the wafer 2.
  • ⁇ is the wavelength of the alignment light.
  • the ⁇ 1-order diffracted lights pass through the reduction lens 3, are reflected by the mirror 51 and directed to the second hologram 82 recorded on the hologram recording medium 8.
  • the second hologram 82 is formed by illuminating the slit 20 arranged at the position corresponding to the surface of the wafer 2 at the incident angle ⁇ .
  • the diffracted light (reproduced light) 511 from the second hologram 82 is focused at the position corresponding to the position of O D shown in FIG. 15C.
  • the reflected light 503 from the wafer 2 illuminates the second hologram 82 and the 0-order light which is not diffracted but transmitted as it is passes through the aperture 521 of the apertured mirror 52.
  • the 1-order diffracted light 511 from the first hologram 81 is reflected at a position O D on the wall other than the aperture 521 of the apertured mirror 52, and focused to the photo-detector 55 by the condenser lens 54.
  • the diffracted light 511 is focused to the photo-detector 55, it produces a detection signal (I) as shown in FIG. 1C.
  • the x-axis position of the alignment mark 21 can be determined.
  • the y-axis position of the alignment mark 21 can be determined by a y-axis detection optical system (not shown).
  • the second hologram 82 is used although it is not necessarily be used. In this case, the 1-order diffracted light or the ⁇ 1-order diffracted lights from the alignment mark 21 are directly detected.
  • FIGS. 2A and 2B Another embodiment of the present invention is explained with reference to FIGS. 2A and 2B.
  • FIGS. 2A and 2B the like elements to those shown in FIGS. 1A to 1D are designated by the like numerals.
  • the slit laser beam 503 for illuminating the alignment mark 21 on the wafer 2 is directed normally to the plane of the alignment mark 21 of the wafer 2 as is done in FIG. 1.
  • the wafer 2 is fixed and the slit laser beam 503 is scanned in the direction E shown in FIG. 2B.
  • the scan of the slit laser beam 503 is attained by deflecting the illumination laser beam 501' by light deflection means.
  • a Galvano-mirror is used as the light deflection means.
  • the Galvano-mirror 57 As the Galvano-mirror 57 is slightly deflected around a z-axis, the position at which the light is focused by the condenser lens 53' is slightly displaced along the y-axis. As a result, the incident angle of the hologram illumination light 501' is slightly changed and the diffracted light 503 from the first hologram 81 forms the slit beam 503 on the wafer 2. It is moved along the x-axis in synchronism with the deflection of the Galvano-mirror 57.
  • the reflected and diffracted light 513 from the alignment mark 21 which has passed through the reduction lens 3 illuminates the second hologram 82 with a slightly varying incident angle. Accordingly, the 1-order diffracted light 512 reproduced by the second hologram 82 is reflected by the beam splitter 56 and passes through the aperture 520 of the apertured mirror 52'.
  • the normal reflected light from the periodic pattern 210 is directed to the first hologram 81, and the 0-order light and 1-order light are blocked by the position O D on the wall of the mirror 52' where the aperture 520 of the mirror 52' is not formed.
  • the 1-order diffracted light from the periodic pattern 210 is directed to the second hologram 82 and blocked by the position O D on the wall of the mirror 52' where the aperture 520 is not formed. As a result, only the diffracted light from the desired periodic pattern 210 passes through the aperture 520 of the mirror 52'.
  • the diffracted light 512 from the desired periodic pattern 210 is focused in the vicinity of the aperture 521. Since the incident angle to the second hologram 82 changes, the focus position varies with the movement of the illumination position of the laser beam 4a to the wafer 2.
  • the diffracted light 512 transmitted through the aperture 520 is focused onto a one-dimension sensor 55' by the focusing lens 550.
  • the image of the alignment mark 21 (image by the 1-order diffracted light) is produced as a signal by deflecting the Galvano-mirror 57 by the drive control circuit 9, reading the image information from the one-dimension sensor 55' and reading the information of the one-dimension sensor 55' after the deflection.
  • FIGS. 3A and 3B Other embodiment of the present invention is explained with reference to FIGS. 3A and 3B.
  • the like elements to those shown in FIGS. 2A and 2B are designated by the like numerals.
  • the alignment mark 21 is of bar shape as shown in FIG. 3B.
  • a chromium film (or chromium oxide film) formed on a periphery of the master pattern 10 of the circuit pattern of the reticle 1 is used as a mirror 51".
  • the illumination light 501' deflected by the Galvano-mirror 57 illuminates the hologram 81, and the diffracted light 502' thereof is reflected by the mirror 51' and the reticle mirror 51", passes through the reduction lens 3 and is directed to the bar alignment mark 21 normally thereto at a varying position.
  • the illumination position to the alignment mark 21 on the wafer 2 is varied by the deflection of the Galvano-mirror 57, and the position at which the diffracted light 502' transmitted through the first hologram 81 and reflected by the beam splitter 56 is focused also varies, and the image of the alignment mark 21 is detected by the one-dimension sensor 55'.
  • the first hologram 81 is used for the illumination and detection and the Galvano-mirror 57 and the one-dimension sensor 55' are driven at the same timing as that of the previous embodiment so that the image of the alignment mark 21 (image by the 1-order diffracted light) is produced as the signal.
  • FIGS. 4A and 4B The like elements to those shown in FIGS. 2A and 3 are designated by the like numerals.
  • three holograms 81, 83 and 83' are recorded on the hologram recording medium 8.
  • the first hologram 81 has the same function as that of the first hologram 81 shown in FIG. 3 and it is used to illuminate the bar alignment mark 21 normally and detect the reflected light therefrom.
  • the second hologram 83 is used to illuminate the bar alignment mark 21 at an incident angle ⁇ as shown in FIG. 4B.
  • the incident light 504 is in the plane of the y-axis and z-axis.
  • the illumination light 504 directed to the wafer at the incident angle ⁇ is reflected by the bar alignment mark 21 at the reflection angle - ⁇ .
  • the reflected light 514 is directed to the third hologram 83' by which it is diffracted. Then, it is reflected by the beam splitter 56, passes through the aperture 510 of the mirror 52' and is focused onto the one-dimension sensor 55'. When it is directed normally to the alignment mark 21 on the wafer 2, it is focused onto the one-dimension sensor 55' through the aperture 510 of the mirror 52' like the case shown in FIG. 4A. Switching between the downward illumination normal to the wafer 2 and the downward illumination at the angle of inclination ⁇ is effected by deflecting the Galvano-mirror 59 by the drive signal from the drive control circuit 9.
  • the alignment mark 21 on the wafer 2 is illuminated normally thereto or at the angle of inclination, and the reflected light 514 therefrom is focused by the one-dimension sensor 55' and the detected signals are added.
  • the asymmetricity of the detection signal waveform for the inclined incident angle due to the ununiformity of application of the resist layer in the vicinity of the alignment mark 21 is substantially reduced by the signal for the normal incident light.
  • JP-A-No. 62-200743 referenced not as prior art but for explanation
  • FIG. 11A shows a thickness of the resist layer 1 versus an interference when the wavelength is 0.515 nm, the detection number of aperture (NA) is 0.42 and the illumination angles are 0° and 23°.
  • the interference intensity does not change significantly with the change in the thickness of the resist layer 1, the affect by the ununiformity of application of the resist layer is low.
  • FIG. 11B shows a drive timing chart for the two Galvano-mirrors 57 and 59, that is, changes in time of deflection angles ⁇ 57 and ⁇ 59. As shown in FIG.
  • FIGS. 5A, 5B and 5C Other embodiment of the present invention is explained with reference to FIGS. 5A, 5B and 5C.
  • the like elements to those shown in FIGS. 3 and 4A are designated by the like numerals.
  • FIG. 5A two laser beams 5031 and 5031' having different wavelengths ⁇ 1 and ⁇ 2 , respectively, are used to detect the alignment mark 21 on the wafer 2.
  • FIG. 5C holograms 821, 822 and 822' for the wavelength ⁇ 1 and holograms 831, 831', 832 and 832' for the wavelength ⁇ 2 are recorded on the hologram recording medium 8.
  • the holograms 821, 822 and 822' for the wavelength ⁇ 1 and holograms 831, 831', 832 and 832' for the wavelength ⁇ 2 are used for illumination, and the hologram 822' for the wavelength ⁇ 1 and the hologram 832' for the wavelength ⁇ 2 are used for detection.
  • the hologram 821 for the wavelength ⁇ 1 is used for illumination and detection.
  • Those seven holograms for the different wavelengths are formed by methods shown in FIGS. 6A and 6B.
  • FIG. 15A shows the method for forming the hologram and the method for using the same for illumination and detection.
  • the holograms 821, 822, 822', 831, 831', 832 and 832' are formed for the wavelength ⁇ 1 of solid line lights 521, 522 and 522' and the wavelength ⁇ 2 of broken line lights 531, 531', 532 and 532'.
  • the image of the alignment mark on the wafer 2 (corresponding to the slit 201 in FIG. 6A) is formed at different position such as A I1 or A I2 as the wavelength ⁇ changes. Those images are reflected by the mirror 51 and focused at A I'l and A I'2 .
  • the reference light 501 having the wavelength ⁇ 1 and the reference light 511 having the wavelength ⁇ 2 are superimposed on the hologram recording medium 8 to form the holograms 821, 822, 822', 831, 831', 832 and 832'.
  • the object light shown in FIG. 6A is a light transmitted through the slit 201, which is generated by illuminating the slit 201 by the light 521 having the waveform ⁇ 1 or the light 531 having the wavelength ⁇ 2 as shown in FIG. 6B.
  • the incident angle ⁇ to the slit 201 is changed as shown in FIG. 6B.
  • the lights 522, 522', 531' and the light 532 and 532' are formed for the wavelengths ⁇ 1 and ⁇ 2 , respectively, and those lights 522, 522', 531', 532 and 532' are directed to the slit 201 and the transmitted light therefrom is used as the object light to form the holograms 822, 822' , 831, 832 and 832'.
  • the reference lights 501 and 511 focused at the position O 1 are used as the reference lights, as they are used when the holograms 821 and 831 are formed. If the reference lights 501 and 511 are directed to other areas than the holograms 822, 822', 831', 832 and 832' to be formed, fogging occurs and this lowers the diffraction efficiency of the other holograms 821 and 831. Accordingly, a mask (not shown) to prevent fogging exposure to the areas other than the desired areas is arranged to face the reticle 1 in the vicinity of the hologram recording medium 8.
  • the holograms 821, 822, 822', 831, 831', 832 and 832' thus formed are arranged in the reducing exposure apparatus as shown in FIGS. 5A and 5B and the reproducing laser beam is directed to those holograms 821, 822, 822', 831, 831', 832 and 832'.
  • the reproducing laser beam is deflected by the Galvano-mirror 57, the illumination beam 5031 is scanned on the alignment mark 21 on the wafer 2 in the direction E shown in FIG. 5B as explained before.
  • the laser beam 5031' reflected by the wafer 2 is detected by the same hologram 821 as that used for the illumination if the angle is 0°, and detected by the hologram which is at a symmetric position with respect to the hologram 821, for example, the hologram 831' when the hologram 831 is used for the illumination, if the angle is larger than 0°. Accordingly, by forming the holograms under the condition shown in Table 1, the asymmeticicity of the detection waveform to the ununiformity of the application of the resist layer is reduced as described in JP-A-No. 62-200743 (referenced not as prior art but for explanation) mentioned above. Accordingly, the detection of the alignment mark 21 with a small detection error is attained.
  • the Galvano-mirror 59 of FIG. 5A is the second Galvano-mirror, which directs the lights having the wavelengths ⁇ 1 and ⁇ 2 simultaneously to the hologram and changes the incident angle to the wafer as the Galvano-mirror 59 is deflected.
  • the holograms 821 and 831 are simultaneously illuminated by the lasers having the wavelengths ⁇ 1 and ⁇ 2 by one deflection angle of the Galvano-mirror 59, and the holograms 822 and 832 are simultaneously illuminated by the lasers having the wavelengths ⁇ 1 and ⁇ 2 by changing the deflection angle of the Galvano-mirror 59. In this manner, the signals detected at two incident angles for two wavelengths ( ⁇ 1 , ⁇ 2 ) are combined and the center position of the combined waveform is determined.
  • FIGS. 12A, 12B and 12C show a change in time of the deflection angles of the two Galvano-mirrors, the incident light to the alignment mark and the reflected light from the alignment mark.
  • the drives of the two Galvano-mirrors and the detector are controlled by the drive control circuit (FIGS. 2A and 4A).
  • the incident angle 3° is angled by 3° with respect to a normal line in a longitudinal direction of the alignment mark 21.
  • 5A is slightly deflected while the two wavelengths ⁇ 1 and ⁇ 2 are directed (t 0 ⁇ t 1 ), and the slit illumination lights 5031 and 5021 drive the alignment mark 21 in the detection direction (arrow in FIG. 5A).
  • the reflected lights 5021' and 5031' from the alignment mark 21 having the wavelengths ⁇ 1 and ⁇ 2 are focused onto the linear sensor 55', and the focusing positions on the linear sensor 55' vary with the scan of the slit illumination lights 5031 and 5021.
  • the Galvano-mirror 59 of FIG. 5A is deflected by a predetermined angle for a time period t 2 ⁇ t 3 to simultaneously illuminate the holograms 822 and 832.
  • the laser beam 5022 having the waveform ⁇ 1 is directed to the alignment mark 21 at the incident angle 20°
  • the laser beam 5032 having the waveform ⁇ 2 is directed at the incident angle 20° so that the detection waveforms for both wavelengths ⁇ 1 and ⁇ 2 are produced.
  • a combined detection strength of four waveforms resulting from the irradiation of the two wavelengths ⁇ 1 and ⁇ 2 to the alignment mark 21 at the two incident angles 0° and 3° varies with the thickness (d) of the resist layer 1 as shown in FIG. 13.
  • the interference intensity variation is small in a range of the thickness d of the resist layer 1 of 1 ⁇ 4.5 ⁇ m, and the interference intensity variation in the range of the thickness d of the resist layer 1 of 1.5 ⁇ 4 ⁇ m is less than 1/5 of the maximum interference intensity variation.
  • FIGS. 14A ⁇ 14C illustrate the reduction of the asymmetricity.
  • FIG. 14A shows the ununiformity of the application of the resist layer 43 on the substrate 42, where the thickness d of the resist layer 43 is 2.3 ⁇ m and the ununiformity of the application is 0.1 ⁇ m.
  • the waveform shown in FIG. 1B is produced.
  • the detection waveform in the present embodiment is shown in FIG. 14C in which the asymmetricity in the detection waveform is significantly low, the distance ⁇ x from the real center of the mark to the center of detection, that is, the detection error is reduced from 0.16 ⁇ m to 0.04 ⁇ m. As a a result, high precision detection is attained.
  • FIG. 7 shows an embodiment which aims to solve the following problem.
  • the spread light is focused by a convex lens 84 to reduce the beam diameter.
  • the visible alignment light 513' emitted from the alignment mark on the wafer 1 (corresponding to the slit 201 of FIG. 8A) is focused by the convex lens 84 to a point A 1 ".
  • Appropriate spread is attained on the hologram recording medium 8 arranged at a mid-point of the focusing point A 1 " and the focusing lens 84.
  • FIG. 8A shows a method for forming a hologram for compensating a wavefront aberration of the reduction lens optical system 3 which includes the convex lens 84.
  • the detection laser beam 513' transmitted through the slit 201 is focused to A 1 " by the convex lens 84.
  • the reference light 501 which is to be focused to a focusing point O 1 is overilluminated in an area which passes through the hologram recording medium 8 arranged in the light path to form the illumination and detection hologram 81 having the wavefront aberration compensation function.
  • FIG. 8B shows a principle of an illumination system which uses the hologram 81 and the convex lens 84 to illuminate the alignment mark 21 of the wafer 2 with the spread corresponding to the width of the slit 201.
  • the wavefront record function of the hologram 81 By using the wavefront record function of the hologram 81, the light 512 which is focused at the point D I and reversely follows the light path of the reference light used to form the hologram 81, the wafer illumination with the narrow range corresponding to the width of the slit is attained.
  • the light 513 irradiated to the alignment mark 21 on the wafer 2 and reflected therefrom passes through the reduction lens 3 and the convex lens 84 as shown in FIG. 8C, is directed to the hologram 81 and the 1-order diffracted light 511 is focused to the focusing point O D .
  • the waveform signal of the alignment mark 21 is detected by the photo-detector 55 as the wafer is scanned in the direction of arrow.
  • FIGS. 9A, 9B and 9C Other embodiment of the present invention is explained with reference to FIGS. 9A, 9B and 9C.
  • the illumination light to the alignment mark of the wafer 20 is different from that of the previous embodiment.
  • the alignment mark illumination light does not illuminate a portion of the alignment mark 21 but widely illuminates the entire alignment mark 21 and the periphery thereof.
  • the illumination light has a wavefront close to that of a collimated light on the surface of the wafer 2.
  • the hologram 85 generates the illumination light.
  • the hologram 85 is formed in a manner shown in FIG. 10D.
  • a pinhole plate 220 is arranged at a position corresponding to the plane of the wafer 2.
  • the pinhole plate 220 has a pinhole 221 having a slightly larger diameter than the width of the wafer alignment mark 21.
  • a narrow collimated laser beam 513'" is irradiated to the pinhole 221 upward through collimeter lenses 231 and 232.
  • the laser beam 513'" transmitted therethrough passes through the reduction lens 3, mirror 51 and convex lens 84, and illuminates the hologram recording medium 8 with a relatively narrow range (because the spread by the diffraction is narrow since the diameter of the pinhole 221 is larger than the slit width).
  • the reference light 501' emitted from the same laser light source is focused by the lens 80 at the focusing point D I and superimposed on the light transmitted through the pinhole, on the hologram 85.
  • the hologram 85 thus formed is reproduced by the reproducing light 505 emitted from the focusing point O I as shown in FIG.
  • FIG. 10A the illumination hologram 85 shown in FIGS. 10A and 10B as well as the hologram 82 (and 1-order diffracted light detecting hologram 82') for detecting the diffracted light 505' from the alignment mark 21 are recorded on the hologram recording medium 8.
  • the hologram 82 is formed by using the convex lens 84, unlike the embodiment of FIG. 1A. As shown in FIG.
  • the hologram 82 is recorded by the reference light 511' having the wavefront of the light transmitted through the slit focused at the point O D .
  • the position of the detection diffracted light O D varies as the slit illumination light 503 (FIG. 2A) scans.
  • the entire alignment mark 21 is illuminated as shown in FIG. 9A and it is detected by the hologram 82 so that the image of the alignment mark by the diffracted light 505' is formed at the position O D .
  • This image is focused on the one-dimension sensor 55' by the focusing lens 550 so that the detection signal of the alignment mark 21 is produced as shown in FIG. 9B.
  • Numeral 52' denotes an apertured mirror.
  • an interference fringe intensity I(x,y) is given by:
  • ⁇ RL (x,y) is a wavefront (phase) after the transmission through the reduction lens
  • ⁇ R (x,y) is a wavefront (phase) of the reference light.
  • the binarized interference image is enlarged at a magnification factor of 5 by the EB drawing apparatus. Since a minimum draw unit is uniquely defined by the EB drawing apparatus, I(x,y) is sampled by the minimum draw unit and the draw data value at each sampling point is compared with the mean intensity (1) to prepare the EB draw data. Based on this data, the reticle is drawn by the EB raw apparatus.
  • the reticle Since the reticle is 5 times as large as the final interference pattern of the hologram, it is mounted on a reticle stage of the reduction exposure apparatus and a glass wafer having resist applied thereon is mounted on a wafer stage, and the interference pattern of the reticle is reduced by a factor of 5.
  • the exposed wafer is developed and the glass wafer is etched to form a desired step pattern to complete the hologram. Since a number of holograms are formed on the glass wafer, it is cut to pieces and one piece is mounted at the hologram position.
  • the interference fringe intensity is expressed as follows instead of the equation (2).
  • a first term in the absolute term of the equation (3) represents a composite amplitude on the hologram after the transmission through the reduction lens
  • a second term represents a complex amplitude of the reference light on the hologram. Since the wavelength of the visible alignment light is approximately two times as large as that of the far ultraviolet exposure light, the alignment light A RL (x,y)exp ⁇ i ⁇ RL (x,y) ⁇ at the hologram position is affected by various aberrations (such as spherical aberration, coma aberration and astigmatism) of the reduction lens so that it is significantly deviated from a uniform plane wave or spherical wave. As a result, A RL (x,y) is not constant as it is in the equation (2) but significantly varies with x and y. In this case, the pattern drawn by the EB is expressed as follows.
  • a ridge of the fringe intensity distribution expressed by the equation (3) is determined as a center of fringe.
  • a width W(x,y) of the fringe (x,y) is determined as a function of A RL (x,y) and A R (x,y).
  • f(A RL , A R : ⁇ ) differs depending on whether the hologram is of amplitude modulation type or phase modulation type.
  • the optimum function of f is chosen depending each of these two types of the holograms.
  • FIG. 16A, 16B and 16C show an embodiment which uses the reflection type hologram.
  • the like elements to those shown in FIG. 15A are designated by the like numerals.
  • FIG. 16A shows a method for forming the reflection type hologram 8'. It is different from the embodiment of FIG. 15A in that the reference light 501' used to form the hologram is directed to the hologram recording medium 8' in the reverse direction to the light 513' transmitted through the reduction lens 3.
  • the reflection type hologram three-dimensionally records the interference fringe created thicknesswise of the hologram on recording medium 8'.
  • the hologram formed in FIG. 16A is used as shown in FIG. 16B so that the alignment mark 21 on the wafer 2 is illuminated by a narrow sheet beam.
  • FIG. 16C shows a method for detecting the light irradiated from the reflection type hologram 8' as the reproduced diffracted light and reflected by the alignment mark 21 on the wafer 2.
  • FIG. 16C shows two detection methods. In one method, the light transmitted through the hologram is detected by the detector 55, and in the other method, the light diffracted by the hologram 86 is detected by the detector 55'. The alignment mark is detected by moving the wafer in the direction E as is done in the embodiment of FIG. 1A.
  • the transmission type hologram is used in the present embodiment
  • the reflection type hologram may be used in the present invention.
  • the illumination light to the alignment mark may be introduced from a clearance between the reduction lens and the wafer to illuminate the alignment mark, and the reflected scattered light from the alignment mark may be detected by using the detection hologram through the reduction lens. In this manner, a high precision alignment mark detection is attained.
  • the wafer alignment mark can be detected through the reduction lens by using the visible light having a sufficiently longer wavelength than that of the exposure light without affecting to the resist layer (fog) or without being affected by the resist layer (the wafer alignment mark is detectable).
  • the alignment mark is detected through the reduction lens, the alignment precision is improved (from 0.15 ⁇ m to 0.08 ⁇ m) and the offset variation is reduced (from 0.05 ⁇ m to 0.03 ⁇ m). If other detection system than the reduction lens is provided, a variation of distance between the reduction lens optical axis and the detection system optical axis due to temperature change or vibration appears as an error as it is.
  • the variation in the detection system before the transmission through the reduction lens due to the temperature change or vibration is reduced to 1/5 (when the reduction lens having the reduction factor of 5 is used) after the transmission through the reduction lens.
  • a light having a short wavelength close to that of the exposure light is used as the alignment detection light, the resist layer is exposed to the illumination light, the illumination light is hard to be transmitted through the resist layer, the level of the detection signal is significantly lowered, proper detector waveform is not produced and the detection precision is lowered.
  • the present invention completely resolve the above problems.
  • the alignment mark on the wafer may be partially exposed to the light to remove the resist by developing.
  • a significant advantage of the present invention is to focus the alignment mark on the wafer without aberration and detect it.
  • the reduction lens exhibits almost non-aberration focusing ability only to the exposure light but exhibits various aberrations to other wavelengths. The problem is severer as the wavelength is farther from the wavelength of the exposure light. It is not impossible to compensate for such aberrations by a lens system but the detection light optical axis does not match to the exposure light optical axis but it inclines relative to the exposure light optical axis. Accordingly, the compensation by the lens system is very difficult to attain.
  • the aberration of the reduction lens is recorded on the hologram by its nature and the wavefront which includes the aberration is reproduced. Accordingly, the illumination and detection of the wafer without aberration (diffraction limit) are attained, and the high resolution detection which could not be attained by the alignment method of the conventional reduction exposure apparatus which uses a g-ray or i-ray reduction lens is attained at the wavelength other than the exposure light wavelength. As a result, the high alignment precision which could not be attained by the prior art reduction exposure apparatus is attained.
  • a light path correction optical system for correcting mismatching of focusing positions due to chromic aberration is used to solve a problem of chromic aberration of the reduction lens caused by two wavelengths.
  • the present alignment method which uses two wavelengths, it is possible to focus the images on one detector by one optical system without requiring additional optical system, and the construction of the apparatus is simplified and the cost is reduced.
  • the affect of the ununiformity of application can be reduced by irradiating laser beams of single wavelength or multi-wavelength at different incident angles and combine the images.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
  • Container, Conveyance, Adherence, Positioning, Of Wafer (AREA)
  • Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
US07/213,141 1987-06-30 1988-06-29 Method and apparatus for optical alignment of semiconductor by using a hologram Expired - Lifetime US4862008A (en)

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Cited By (14)

* Cited by examiner, † Cited by third party
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US4964698A (en) * 1989-09-22 1990-10-23 Amp Incorporated System for selective laser assisted plating
US5324953A (en) * 1992-02-05 1994-06-28 Hitachi, Ltd. Reduced-projection exposure system with chromatic aberration correction system including diffractive lens such as holographic lens
US5430548A (en) * 1992-02-06 1995-07-04 Hitachi, Ltd. Method and apparatus for pattern detection
WO1996000912A3 (en) * 1994-06-30 1996-05-23 Univ North Carolina Achromatic optical system including diffractive optical element, and method of forming same
US5684569A (en) * 1993-12-22 1997-11-04 Nikon Corporation Position detecting apparatus and projection exposure apparatus
US5808724A (en) * 1995-03-24 1998-09-15 Canon Kabushiki Kaisha Illumination method and system having a first optical element at a position optically conjugate with an object and a second optical element closer to the object and on a pupil plane of the system
US5999270A (en) * 1995-04-13 1999-12-07 Canon Kabushiki Kaisha Projection exposure apparatus and microdevice manufacturing method using the same
WO2000055674A1 (en) * 1999-03-17 2000-09-21 Rochester Institute Of Technology Mofification of a projection imaging system with a non-circular aperture and a method thereof
US6396569B2 (en) 1999-09-02 2002-05-28 Texas Instruments Incorporated Image displacement test reticle for measuring aberration characteristics of projection optics
US6704089B2 (en) * 2000-04-28 2004-03-09 Asml Netherlands B.V. Lithographic projection apparatus, a method for determining a position of a substrate alignment mark, a device manufacturing method and device manufactured thereby
US20050040443A1 (en) * 2003-08-21 2005-02-24 Andreas Michael T. Wafer cleaning method and resulting wafer
US20110085726A1 (en) * 2009-04-09 2011-04-14 Asml Holding N.V. Tunable Wavelength Illumination System
TWI418759B (zh) * 2009-03-24 2013-12-11 佳能股份有限公司 位置偵測設備、曝光設備及裝置製造方法
US11022772B2 (en) 2016-03-23 2021-06-01 United Kingdom Research And Innovation Laser-chain alignment

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JPS60124645A (ja) * 1983-12-09 1985-07-03 Mitsubishi Petrochem Co Ltd ガラス繊維強化樹脂組成物
JP2728917B2 (ja) * 1989-02-13 1998-03-18 株式会社日立製作所 パターン検出方法及びその装置並びに投影露光装置
JPH0621207B2 (ja) * 1990-01-30 1994-03-23 出光石油化学株式会社 ポリオレフィン樹脂組成物
JP2574619B2 (ja) * 1993-01-29 1997-01-22 松下電器産業株式会社 露光装置

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Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4964698A (en) * 1989-09-22 1990-10-23 Amp Incorporated System for selective laser assisted plating
US5324953A (en) * 1992-02-05 1994-06-28 Hitachi, Ltd. Reduced-projection exposure system with chromatic aberration correction system including diffractive lens such as holographic lens
US5430548A (en) * 1992-02-06 1995-07-04 Hitachi, Ltd. Method and apparatus for pattern detection
US5684569A (en) * 1993-12-22 1997-11-04 Nikon Corporation Position detecting apparatus and projection exposure apparatus
WO1996000912A3 (en) * 1994-06-30 1996-05-23 Univ North Carolina Achromatic optical system including diffractive optical element, and method of forming same
US5606434A (en) * 1994-06-30 1997-02-25 University Of North Carolina Achromatic optical system including diffractive optical element
US5808724A (en) * 1995-03-24 1998-09-15 Canon Kabushiki Kaisha Illumination method and system having a first optical element at a position optically conjugate with an object and a second optical element closer to the object and on a pupil plane of the system
US5999270A (en) * 1995-04-13 1999-12-07 Canon Kabushiki Kaisha Projection exposure apparatus and microdevice manufacturing method using the same
US6541750B1 (en) 1999-03-17 2003-04-01 Rochester Institute Of Technology Modification of a projection imaging system with a non-circular aperture and a method thereof
WO2000055674A1 (en) * 1999-03-17 2000-09-21 Rochester Institute Of Technology Mofification of a projection imaging system with a non-circular aperture and a method thereof
US6396569B2 (en) 1999-09-02 2002-05-28 Texas Instruments Incorporated Image displacement test reticle for measuring aberration characteristics of projection optics
US6704089B2 (en) * 2000-04-28 2004-03-09 Asml Netherlands B.V. Lithographic projection apparatus, a method for determining a position of a substrate alignment mark, a device manufacturing method and device manufactured thereby
US20040095565A1 (en) * 2000-04-28 2004-05-20 Asml Netherlands B.V. Lithographic projection apparatus, a method for determining a position of a substrate alignment mark, a device manufacturing method and device manufactured thereby
US6987556B2 (en) 2000-04-28 2006-01-17 Asml Netherlands B.V. Lithographic projection apparatus, a method for determining a position of a substrate alignment mark, a device manufacturing method and device manufactured thereby
US20050040443A1 (en) * 2003-08-21 2005-02-24 Andreas Michael T. Wafer cleaning method and resulting wafer
US7023099B2 (en) * 2003-08-21 2006-04-04 Micron Technology, Inc Wafer cleaning method and resulting wafer
TWI418759B (zh) * 2009-03-24 2013-12-11 佳能股份有限公司 位置偵測設備、曝光設備及裝置製造方法
US20110085726A1 (en) * 2009-04-09 2011-04-14 Asml Holding N.V. Tunable Wavelength Illumination System
US8508736B2 (en) * 2009-04-09 2013-08-13 Asml Holding N.V. Tunable wavelength illumination system
US8730476B2 (en) 2009-04-09 2014-05-20 Asml Holding N.V. Tunable wavelength illumination system
US11022772B2 (en) 2016-03-23 2021-06-01 United Kingdom Research And Innovation Laser-chain alignment

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